RNAi-mediated suppression of isoprene emission in poplar transiently impacts phenolic metabolism under high temperature and high light intensities: a transcriptomic and metabolomic analysis

Abstract

In plants, isoprene plays a dual role: (a) as thermo-protective agent proposed to prevent degradation of enzymes/membrane structures involved in photosynthesis, and (b) as reactive molecule reducing abiotic oxidative stress. The present work addresses the question whether suppression of isoprene emission interferes with genome wide transcription rates and metabolite fluxes in grey poplar (Populusxcanescens) throughout the growing season. Gene expression and metabolite profiles of isoprene emitting wild type plants and RNAi-mediated non-isoprene emitting poplars were compared by using poplar Affymetrix microarrays and non-targeted FT-ICR-MS (Fourier transform ion cyclotron resonance mass spectrometry). We observed a transcriptional down-regulation of genes encoding enzymes of phenylpropanoid regulatory and biosynthetic pathways, as well as distinct metabolic down-regulation of condensed tannins and anthocyanins, in non-isoprene emitting genotypes during July, when high temperature and light intensities possibly caused transient drought stress, as indicated by stomatal closure. Under these conditions leaves of non-isoprene emitting plants accumulated hydrogen peroxide (H2O2), a signaling molecule in stress response and negative regulator of anthocyanin biosynthesis. The absence of isoprene emission under high temperature and light stress resulted transiently in a new chemo(pheno)type with suppressed production of phenolic compounds. This may compromise inducible defenses and may render non-isoprene emitting poplars more susceptible to environmental stress.Electronic supplementary materialThe online version of this article (doi:10.1007/s11103-010-9654-z) contains supplementary material, which is available to authorized users.

Modulation of Protein S-Nitrosylation by Isoprene Emission in Poplar

“…The lower amount of protein members of the photosynthetic apparatus may influence the physiology of NE poplar under unstressed conditions and upon stress. While initial physiological measurements showed no significant differences in the net CO 2 assimilation rates of both genotypes (Behnke et al, 2007(Behnke et al, , 2009(Behnke et al, , 2010a, recent observations reported lower gas exchange (Way et al, 2013) and electron transport rates (Velikova et al, 2015) in the NE genotype compared with the IE genotype.…”

“…Plants that were fumigated with isoprene showed less visible ultrastructural (chloroplast) damage and less impairment of photosynthetic processes upon acute ozone fumigation than plants where isoprene was absent ). In conjunction with this hypothesis, leaf levels of hydrogen peroxide (H 2 O 2 ; Loreto and Velikova, 2001;Behnke et al, 2010a), singlet oxygen (Affek and Yakir, 2002;Velikova, et al, 2004), and the free radical nitric oxide (NO; were found to be lower in stressed plants when leaf internal isoprene was present. Taken together, these findings strongly indicate that endogenous isoprene modulates the oxidative and nitrosative load in plant tissue upon abiotic stress.…”

Facing the Future: Effects of Short-Term Climate Extremes on Isoprene-Emitting and Nonemitting Poplar

“…In addition to the general physiological performance of Grey poplar under predicted future short-term extremes, we also aimed to quantify the environmental impact on transgenic poplar genotypes with an almost complete absence of isoprene emission (Behnke et al, 2007(Behnke et al, , 2010a. This interest is motivated by the proposed function of isoprene in plant stress mitigation (Loreto and Schnitzler, 2010) and the potential for biotechnological generation or the phenotyping of low-isopreneemitting or NE poplars as a strategy to minimize the harmful effects of large poplar plantations on local air quality and human health (Ainsworth et al, 2012;Rosenkranz et al, 2014).…”

Early Induction of Apple Fruitlet Abscission Is Characterized by an Increase of Both Isoprene Emission and Abscisic Acid Content

“…The cv Red Chief statistics are reported in Supplemental Table S2. Given that the protonated mass 69 in plants has been unambiguously identified as isoprene Cinege et al, 2009;Behnke et al, 2010;Rasulov et al, 2010), whereas the other masses with high Z scores have not always been precisely identified, attention was focused on isoprene. However, because the emission of this volatile compound by apple fruitlets has not yet been reported, specific investigations were conducted by means of gas chromatography-mass spectrometry with a flame ionization detector, and additional measurements were performed by PTR-MS on ionization spectra as a function of collision energy to confirm the identity of m/z 69.…”